INTRODUCTION. 5 which contain only a small percentage. In irons used for making steel by the usual Bessemer process, the iron is not allowed to contain over one-tenth of one per cent, of phosphorus. For basic steel and for foundry work no fixed limit can be given. Where great toughness is required in iron castings it is well to use what is called "Bessemer pig-iron," by which term is meant an iron containing not over one-tenth of one per cent, of phosphorus. Such an iron costs very little more than ordinary foundry grades. In other cases a high percentage is desired to confer great fluidity, and irons carrying 3 per cent, of phosphorus are in demand, a certain proportion of such metal being used in making intricate castings where the metal must accurately fill every corner of the mold. Pure iron itself is very difficult to melt; it is soft, tough and malleable both hot and cold, but the elements above described, preeminently the presence of nearly 4 per cent, of carbon, change its character completely in the following ways: (1) It is more fusible. (2) It is brittle. (3) It cannot be forged either hot or cold. Thus we have what the general public calls cast-iron. In the trade, however, this term is applied to it only after it has been melted again and cast into some finished form. The product of the blast-furnace is always spoken of as pig-iron. It is the foundation stone of all the iron industry; it is one of the great staples in the commerce of the world. The foundryman makes from it his kettles and stoves; the puddler refines it and supplies the village blacksmith with bars for chains and horseshoes; the steel maker transmutes it into watch-springs and cannon. THE MAKING OP WEOUGHT-IKOK When the Bessemer process of steel making was invented it was confidently predicted that it sounded the death-knell of the puddling furnace, but although there have been several announcements of the funeral, the great event has never actually occurred. There seem to be a few places where wrought-iron is needed, and there are many more places where the blacksmith and the machinist find steel unsatisfactory, because they do not know anything about the. metal and refuse to learn, usually stating that they have been "working long enough to know."